A leading Tory activist has predicted that David Cameron will again fail to win a solid majority at the next election and would rather forge a second coalition with the Liberal Democrats than rely on the support of the significant number of his own MPs who do not trust him or see him as "one of them".

He said there was a "problem of trust" between a significant number of Tory backbenchers and the prime minister, despite a six-month "charm offensive" by Cameron as he attempted to close the gap between them.

"If you are out on the front line in the war you want to know the staff officers are completely on your side. And for some of those people on the front line there is a question mark about that.

"And don't neglect the obvious - that he is not a proven winner," he said.

He also repeated fears over the potential influx of immigrants from Romania and Bulgaria next year, highlighted by a poll for the Daily Mail suggesting 82% of voters want it blocked, and said the issue should be a red line in the prime minister's negotiations with Brussels.

If Cameron failed to get changes allowing Britain to control its borders, he should then reverse his current position and recommend Britain pulls out of the EU in a referendum.

Speaking about the general election, Goodman said: "Because of the way the demographics work, the impact of Ukip and because of left-wing LibDem voters going off to Labour, it's extremely unlikely there will be Conservative majority in 2015.

"The range of possibilities is between a solid Labour majority and a Cameron- led minority government, or a coalition with the Conservatives as the biggest party coming back with a similar or slightly better result that they got in 2010," he said

Of the two options facing Cameron, he would favour another coalition because he would not want to be "dependent on the votes of people who distrust him and, in some cases, dislike him," he said.

Goodman's remarks echo concerns that have been rumbling around the Tory party and Cameron's leadership for some time but which have been thrown into sharp focus by Ed Miliband's recent success in seizing the political advantage.

It has led to senior Tories speaking out about the direction the party should be taking in the run-up to the next election with some, like arch moderniser Nick Boles, urging a revival of the socially liberal aspects of Cameron's agenda.

Goodman, whose website provides a widely read and highly influential forum for debate amongst Tory grassroots members and the leadership, said he believed Cameron should instead be focussing on the key issues that were affecting people today - notably homes, jobs and savings.

While immigration was not as important an issue for voters at election time as often claimed, "there is reason to believe it might be different this time," he said, so Cameron needed to make it central to his negotiations over the future of the EU and Britain's place within it.

And he urged the prime minister to reach out more to all wings of the party, including those often deemed to be on the right.

"Successful Conservative leaders here and abroad - Margaret Thatcher, Stephen Harper in Canada, Tony Abbott and John Howard in Australia - have all run their parties as a broad church and sought to appeal to their right as well as their centre," he said.